The present invention relates to search type tuning systems.
A wide variety of "search" or "signal seeking" tuning systems for radio and television receivers are known which provide for automatically tuning only those channels which have acceptable reception characteristics and for skipping past those channels which have unacceptable reception characteristics. Such tuning systems typically include a number of signal detectors for determining when a received RF carrier has acceptable reception characteristics. For example, a search type tuning system for a television receiver may include: an AFT (automatic fine tuning) detector for determining when an IF carrier derived from the received RF carrier has a frequency within a predetermined range of its desired value; and AGC (automatic gain control) detector for determining when the received RF carrier has an amplitude greater than a predetermined value; and a synchronization detector to determine when synchronization pulses derived from the received RF carrier have the proper frequency.
Tuning systems are also known which include a memory having memory locations associated with each channel in a tuning range for storing information as to whether the associated station or channel is preferred or not. Such "memory" type tuning systems may be utilized as an alternative to the "search" type tuning systems to select only those channels with acceptable reception characteristics in a given location.
Both "search" and "memory" type tuning systems require a considerable amount of complex and expensive circuitry, in addition to the basic tuning system for tuning each channel in a tuning range, for tuning only those channels with acceptable reception characteristics. Thus, there is a need for a tuning system which requires only a relatively small amount of circuitry in addition to the basic tuning system for tuning only channels with acceptable reception characteristics.